What to wear to Lollapalooza: Chicago sits at 29°C (84°F) by day and 20°C (68°F) at night in August, on city park, with a moderate chance of rain. That means a light base with one warm layer you can carry, cushioned trainers or a low boot, and a bag small enough for the gate rules. The crowd leans streetwear, y2k and pop, so anything that survives the day reads as right.
Women's outfits at Lollapalooza have to clear the same three hurdles as everyone else's. 29°C (84°F) by day, 20°C (68°F) at night, city park underfoot, with more options for solving them.
The dominant aesthetics at Lollapalooza are streetwear, Y2K revival, pop and indie. That is the visual language of the site, the stages, the merch, the crowd photos, and outfits that speak it look intentional rather than borrowed.
There is no enforced dress code. What the crowd rewards is a look that survives 4 days of city park without you having to protect it.
What people actually wear: one good layer over a light base, because the temperature halves after sunset; something identifiable, a colour, a hat, a flag, so your group can find you in a crowd of that size.